The present application relates to a color conversion element used for a liquid crystal display or the like and a display unit.
In the past, as a thin display unit, a liquid crystal display (LCD) has been used. In the liquid crystal display, a backlight irradiating the whole area of a liquid crystal panel from behind is used. The liquid crystal displays are classified broadly into direct lighting type and edge lighting type according to the structure of the backlight. In the edge lighting type, after light entering from the side face of a light guide plate is propagated inside the light guide plate, the light is extracted from the top face of the light guide plate. Meanwhile, in the direct lighting type, for example, a plurality of fluorescent lamps such as a CCFL (Cols Cathode Fluorescent Lamp) are arranged on a substrate, and thereby surface light emission is made as a whole (for example, see Japanese Unexamined Patent Application Publication No. 2005-108635).
In recent years, the liquid crystal display has been gotten larger, thinned, and lightened, and the life thereof has been lengthened. Further, in terms of improving moving picture characteristics by blinking control, a light emitting unit for performing surface light emission by arranging a plurality of light emitting diodes (LED) on a substrate has attracted attention. In such a light emitting unit, the following two methods are mainly used for extracting white light. In the first method, light emitting diodes that respectively emit each color of three colors R, G, and B are arranged, such light emitting diodes are concurrently lighted, and thereby the three color light is synthesized to obtain white light. In the second method, for example, a blue light emitting diode chip is surrounded by a resin containing a phosphor, and blue light is color-converted to white light.
However, in the foregoing second method, potting of the phosphor is made for a minute area of the light emitting diode chip. Thus, it is difficult to evenly and uniformly form the resin containing the phosphor. Thus, in recent years, as the third method replacing the second method, a method of color-converting blue light by using a material in which the resin containing the phosphor is sandwiched between a sheet base material (hereinafter referred to as a phosphor sheet) has attracted attention.
Meanwhile, in general, the phosphor is weak to oxygen and moisture vapor. When the phosphor is exposed to oxygen, moisture vapor and the like, the characteristics thereof are deteriorated. Thus, in the case where the phosphor sheet is used for the backlight, luminance and chromaticity deteriorates. Such deterioration of the phosphor is particularly significant under high temperature and high humidity environment. Thus, in the foregoing phosphor sheet, high moisture vapor barrier properties, high gas barrier properties and the like are needed for the sheet base material.
Thus, a method of providing a protective layer composed of a silicon compound or the like on the resin containing the phosphor (see Japanese Examined Patent Application Publication No. 6-58440) and a method of directly coating the surface of the resin containing the phosphor with a protective embrocation (refer to Japanese Unexamined Patent Application Publication No. 59-42500) have been proposed. Further, a method of sealing the resin containing the phosphor by sandwiching with two pieces of glass plates has been also proposed (see Japanese Unexamined Patent Application Publication No. 2007-23267).